Characterizing gravitational instability in turbulent multi-component galactic discs

Gravitational instabilities play an important role in galaxy evolution and in shaping the interstellar medium (ISM). The ISM is observed to be highly turbulent, meaning that observables like the gas surface density and velocity dispersion depend on the size of the region over which they are measured. In this work we investigate, using simulations of Milky Way-like disc galaxies with a resolution of $\sim 9$ pc, the nature of turbulence in the ISM and how this affects the gravitational stability of galaxies. By accounting for the measured average turbulent scalings of the density and velocity fields in the stability analysis, we can more robustly characterize the average level of stability of the galaxies as a function of scale, and in a straightforward manner identify scales prone to fragmentation. Furthermore, we find that the stability of a disc with feedback-driven turbulence can be well described by a "Toomre-like" $Q$ stability criterion on all scales, whereas the classical $Q$ can formally lose its meaning on small scales if violent disc instabilities occur in models lacking pressure support from stellar feedback.Comment: 11 pages, 5 figures, submitted to MNRA

The effects of catecholamines on protein metabolism in pigs and sheep

Using a constant infusion of 1-(\u2714)C leucine and 4,5-(\u273)H (alpha)-ketoisocaproate (KIC), the rates of whole-body leucine and KIC metabolism were estimated in pigs during acute infusions of epinephrine (EPI) and norepinephrine (NOR), and in sheep during acute infusins of EPI, NOR and a specific (beta)(,2)-adrenergic agonist, cimaterol (CIM). The pigs and sheep responded similarly to EPI, with decreased rates of leucine entry (proteolysis in the pigs, and proteolysis and absorption of amino acids in the sheep) and protein synthesis. EPI infusion in the sheep also resulted in increases in leucine and KIC interconversion. NOR infusion produced decreases in the rates of proteolysis, protein synthesis, leucine and KIC interconversion, and KIC oxidation in the pigs, but had no significant effect on protein metabolism in the sheep. Acute infusions of CIM in the sheep resulted in decreases in the rates of leucine entry, protein synthesis and reamination of KIC to leucine. Glucose concentrations rose during all infusions, while free fatty acid (FFA) levels were elevated during NOR infusion in both species and during EPI infusion in the sheep. Insulin concentrations increased during the infusion of all adrenergic agents in sheep, but did not change in the pigs. Plasma glucagon concentrations increased during the EPI infusion in the sheep and the NOR infusion in the pigs, but decreased during the CIM infusion. Cortisol concentrations rose during NOR infusion in both species, but were unaffected by the other treatments. Despite a general increase in insulin to glucagon ratios with catechol infusion, whole-body protein anabolism was not evident in these acute studies. Differences may exist, however, in individual tissues which may change the distribution of body proteins. The changes in metabolite concentrations in the plasma indicate that acute infusions of these compounds increase the supply of readily available energy in the plasma. The supply of energy would be further supplemented as a result of the reduction in protein turnover seen in these experiments

Rise Overrun: Condoization, Gentrification, and the Changing Political Economy of Renting in Toronto

Privately owned high-rise condominiums have been increasing as a proportion of all housing units built in the Greater Toronto Area for many decades. This has inspired a growing literature theorizing both “condoism” as an emergent planning-development regime and the implications of “condoization” and “condofication” for urban governance and everyday life in cities like Toronto. Building on this literature, this article assesses the implications of Toronto’s increasing reliance on (mainly vertical) condominium development for the socio-spatial transformation of the housing market, particularly for renters. Analyzing time-series data from Canada Mortgage and Housing Corporation and the Census of Canada to quantify the effects of the city’s condoization, we answer three key questions: How important is condominium development for understanding the restructuring of Toronto’s economy? How has condoization contributed to the ongoing gentrification of Toronto’s inner city? How is condoization restructuring Toronto’s rental market? Building on previous research categorizing and mapping the gentrification of Toronto’s inner city, we find that condoization is an increasingly defining element restructuring the city’s rental market, while this restructuring also plays a central role in the advancing gentrification of the city’s core

Examining Two Self-Assessment Measures of Teacher Multicultural Competence and Their Predictive Value to Student Behavior Outcomes

Multicultural competence is a construct that has been discussed in the education literature as an essential skill for teachers\u27 success in reaching all children in the classroom. The current study advances the literature on multicultural competence, specifically pertaining to teachers within their classrooms. Additional evidence was found building upon the technical adequacy of two, theoretically different, measures of teacher multicultural competence. Teachers who received a greater number of hours of multicultural training had significantly higher self-efficacy regarding engaging in culturally responsive teaching practices, than those who had received fewer hours. This study also replicated previous research (Hamilton, 2016) finding that teachers who shared an ethnic match with the majority of their classroom reported higher scores of student/classroom engagement and lower scores of teacher burnout. Interestingly, measures of multicultural competence did not demonstrate significant predictive validity for teachers\u27 self-reported use of exclusionary discipline. Possible explanations, implications, and future directions are discussed

Succession and Transfer of Businesses in Canada

Canada is a liberal market economy and as such the freedom of owners of capital to transfer businesses is not heavily regulated and the rights of workers affected by those transfers are limited. Before discussing those rights some preliminary matters need to be addressed

Dismissal Due to Business Reasons in Canada

Canada is a liberal market economy and as such the law places few restrictions on the employer’s freedom to dismiss an employee. In particular, the law places no restriction on the freedom of employers to dismiss employees for business reasons. However, dismissed employees are entitled to certain rights, the most important of which is notice of termination or pay in lieu of notice

Conceptual Change: Gods, Elements, and Water

On what does the meaning of the concept of water depend? I consider three possible answers: the physical world, theory, or both the physical world and theory. Each answer supports a particular history. If the history unique to an answer is confirmed by the actual history of the concept of water, then there is supporting evidence for that account of meaning. I have documented the historical development of the concept of water, focusing on three periods: the ancient Greeks, the 18th and 19th centuries, and the 20th and 21st centuries. Conceptual change figures prominently in that history, and when enough historical data are available communication across theories is obvious. Those features suggest that the meaning of the concept of water depends on the physical world and the theory in which it is embedded. The physical world explains cross theory communication; and theory accounts for the conceptual changes that I have documented. The history of the concept of water suggests that Putnam (1975) is right: meaning depends on the physical world and the theory in which it is embedded. He’s right, however, for the wrong reasons. Putnam relies on a thought experiment to demonstrate that the physical world contributes to meaning, but the history suggests that he built some chemically implausible assumptions into that thought experiment

Physical properties and scaling relations of molecular clouds: the effect of stellar feedback

Using hydrodynamical simulations of entire galactic discs similar to the Milky Way, reaching 4.6pc resolution, we study the origins of observed physical properties of giant molecular clouds (GMCs). We find that efficient stellar feedback is a necessary ingredient in order to develop a realistic interstellar medium (ISM), leading to molecular cloud masses, sizes, velocity dispersions and virial parameters in excellent agreement with Milky Way observations. GMC scaling relations observed in the Milky Way, such as the mass-size ($M$--$R$), velocity dispersion-size ($\sigma$--$R$), and the $\sigma$--$R\Sigma$ relations, are reproduced in a feedback driven ISM when observed in projection, with $M\propto R^{2.3}$ and $\sigma\propto R^{0.56}$. When analysed in 3D, GMC scaling relations steepen significantly, indicating potential limitations of our understanding of molecular cloud 3D structure from observations. Furthermore, we demonstrate how a GMC population's underlying distribution of virial parameters can strongly influence the scatter in derived scaling relations. Finally, we show that GMCs with nearly identical global properties exist in different evolutionary stages, where a majority of clouds being either gravitationally bound or expanding, but with a significant fraction being compressed by external ISM pressure, at all times.Comment: 12 pages, 8 figures, accepted for publication in Monthly Notices of the Royal Astronomical Societ

On the Observed Diversity of Star Formation Efficiencies in Giant Molecular Clouds

Observations find a median star formation efficiency per free-fall time in Milky Way Giant Molecular Clouds (GMCs) on the order of $\epsilon_{\rm ff}\sim 1\%$ with dispersions of $\sim0.5\,{\rm dex}$. The origin of this scatter in $\epsilon_{\rm ff}$ is still debated and difficult to reproduce with analytical models. We track the formation, evolution and destruction of GMCs in a hydrodynamical simulation of a Milky Way-like galaxy and by deriving cloud properties in an observationally motivated way, measure the distribution of star formation efficiencies which are in excellent agreement with observations. We find no significant link between $\epsilon_{\rm ff}$ and any measured global property of GMCs (e.g. gas mass, velocity dispersion). Instead, a wide range of efficiencies exist in the entire parameter space. From the cloud evolutionary tracks, we find that each cloud follow a \emph{unique} evolutionary path which gives rise to wide diversity in all properties. We argue that it is this diversity in cloud properties, above all else, that results in the dispersion of $\epsilon_{\rm ff}$.Comment: 10 pages, 6 figures, accepted for publication in Monthly Notices of the Royal Astronomical Societ